Fact: That is a random number. There is not a lot of hard-core evidence that you have to drink this amount. Healthy adults should actually consume about 91 ounces of water a day – but that includes intake from all beverages and food, not just what goes into your water glass. Still, that is only an estimate. You might need more if you live in a hot and humid climate, exercise a ton or are pregnant. Most healthy adults will hit the right amount by following their own thirst cues.

Bottom Line: As long as you drink when you are thirsty (notice a theme here?) and your pee is generally pale yellow, it is not necessary to count your ounces.